nixos/grafana: document how to enable drilldown when using custom plugins

IMHO, it's a bit surprising that drilldown doesn't show anything when
using `declarativePlugins` (and thus, the four apps are missing).

Add instructions on how to get these apps back.

Changed files
+8 -1
nixos
modules
services
monitoring
+8 -1
nixos/modules/services/monitoring/grafana.nix
···
declarativePlugins = mkOption {
type = with types; nullOr (listOf path);
default = null;
-
description = "If non-null, then a list of packages containing Grafana plugins to install. If set, plugins cannot be manually installed.";
example = literalExpression "with pkgs.grafanaPlugins; [ grafana-piechart-panel ]";
# Make sure each plugin is added only once; otherwise building
# the link farm fails, since the same path is added multiple
···
declarativePlugins = mkOption {
type = with types; nullOr (listOf path);
default = null;
+
description = ''
+
If non-null, then a list of packages containing Grafana plugins to install. If set, plugins cannot
+
be manually installed.
+
+
Keep in mind that this turns off drilldown: for this to work, you need to add
+
`grafana-metricsdrilldown-app`, `grafana-lokiexplore-app`, `grafana-exploretraces-app`
+
and `grafana-pyroscope-app` to this option.
+
'';
example = literalExpression "with pkgs.grafanaPlugins; [ grafana-piechart-panel ]";
# Make sure each plugin is added only once; otherwise building
# the link farm fails, since the same path is added multiple